Abstract:

A chemically amplified positive resist composition comprising: a resin
comprising a structural unit having an acid-labile group in a side chain
and an acid generator wherein the resin contains 40 to 90% by mole of the
structural unit having an acid-labile group in a side chain based on all
the structural units and the structural unit having an acid-labile group
in a side chain contains a structural unit represented by the formula
(I):
##STR00001##
wherein R1 represents a hydrogen atom or a methyl group, Z represents
a single bond or --(CH2)k--CO--O--, k represents an integer of
1 to 4, R2 is independently in each occurrence a C1-C6 alkyl group,
and m represents an integer of 0 to 14.

Claims:

1. A chemically amplified positive resist composition comprising: a resin
comprising a structural unit having an acid-labile group in a side chain
and an acid generator wherein the resin contains 40 to 90% by mole of the
structural unit having an acid-labile group in a side chain based on
total molar amounts of all the structural units and the structural unit
having an acid-labile group in a side chain contains a structural unit
represented by the formula (I): ##STR00164## wherein R1 represents a
hydrogen atom or a methyl group, Z represents a single bond or
--(CH2)k--CO--O--, k represents an integer of 1 to 4, R2
is independently in each occurrence a C1-C6 alkyl group, and m represents
an integer of 0 to 14.

2. The chemically amplified positive resist composition according to claim
1, wherein the resin contains 50 to 70% by mole of the structural unit
having an acid-labile group in a side chain based on total molar amounts
of all the structural units.

3. The chemically amplified positive resist composition according to claim
1, wherein the structural unit having an acid-labile group in a side
chain further contains a structural unit represented by the formula (II):
##STR00165## wherein R3 represents a hydrogen atom or a methyl
group, Z1 represents a single bond or --(CH2)j--CO--O--, j
represents an integer of 1 to 4, R4 represents a C1-C8 alkyl group
or a C3-C8 cycloalkyl group, and ring Z2 represents an unsubstituted
or substituted C3-C30 cyclic hydrocarbon group, in addition to the
structural unit represented by the formula (I), with the proviso that the
structural unit represented by the formula (II) is different from the
unit represented by the formula (I).

4. The chemically amplified positive resist composition according to claim
1, wherein the resin further contains a structural unit represented by
the formula (IV): ##STR00166## wherein R12 represents a hydrogen
atom or a methyl group, Z3 represents a single bond or
--(CH2)i--CO--O--, i represents an integer of 1 to 4, and ring
Z4 represents an unsubstituted or substituted C3-C30 cyclic
hydrocarbon group having --CO--O-- in the ring structure.

5. The chemically amplified positive resist composition according to claim
1, wherein the acid generator is an acid generator represented by the
formula (V): ##STR00167## wherein Y1 and Y2 each independently
represent a fluorine atom or a C1-C6 perfluoroalkyl group, R40
representsa C1-C36 hydrocarbon group which may have at least one selected
from the group consisting of a C1-C6 alkoxy group, a C1-C4 perfluoroalkyl
group, a C1-C6 hydroxyalkyl group, a hydroxyl group and a cyano group,
and one or more --CH2-- in the hydrocarbon group may be replaced by
--CO--, --O-- or --COO--, and A+ represents an organic counter ion.

[0007]The present invention relates to the followings: [0008]<1> A
chemically amplified positive resist composition comprising: a resin
comprising a structural unit having an acid-labile group in a side chain
and an acid generator wherein the resin contains 40 to 90% by mole of the
structural unit having an acid-labile group in a side chain based on
total molar amounts of all the structural units and the structural unit
having an acid-labile group in a side chain contains a structural unit
represented by the formula (I):

##STR00002##

[0008]wherein R1 represents a hydrogen atom or a methyl group, Z
represents a single bond or --(CH2)k--CO--O--, k represents an
integer of 1 to 4, R2 is independently in each occurrence a C1-C6
alkyl group, and m represents an integer of 0 to 14; [0009]<2> The
chemically amplified positive resist composition according to <1>,
wherein the resin contains 50 to 70% by mole of the structural unit
having an acid-labile group in a side chain based on total molar amounts
of all the structural units; [0010]<3> The chemically amplified
positive resist composition according to <1> or <2>, wherein
the structural unit having an acid-labile group in a side chain further
contains a structural unit represented by the formula (II):

##STR00003##

[0010]wherein R3 represents a hydrogen atom or a methyl group,
Z1 represents a single bond or --(CH2)j--CO--O--, j
represents an integer of 1 to 4, R4 represents a C1-C8 alkyl group
or a C3-C8 cycloalkyl group, and ring Z2 represents an unsubstituted
or substituted C3-C30 cyclic hydrocarbon group, in addition to the
structural unit represented by the formula (I), with the proviso that the
structural unit represented by the formula (II) is different from the
unit represented by the formula (I); [0011]<4> The chemically
amplified positive resist composition according to <1>, <2>
or <3>, wherein the resin further contains a structural unit
represented by the formula (IV):

##STR00004##

[0011]wherein R12 represents a hydrogen atom or a methyl group,
Z3 represents a single bond or --(CH2)i--CO--O--, i
represents an integer of 1 to 4, and ring Z4 represents an
unsubstituted or substituted C3-C30 cyclic hydrocarbon group having
--CO--O-- in the ring structure; [0012]<5> The chemically amplified
positive resist composition according to any one of <1> to
<4>, wherein the acid generator is an acid generator represented by
the formula (V):

##STR00005##

[0012]wherein Y1 and Y2 each independently represent a fluorine
atom or a C1-C6 perfluoroalkyl group, R40 represents a C1-C36
hydrocarbon group which may have at least one selected from the group
consisting of a C1-C6 alkoxy group, a C1-C4 perfluoroalkyl group, a C1-C6
hydroxyalkyl group, a hydroxyl group and a cyano group, and one or more
--CH2-- in the hydrocarbon group may be replaced by --CO--, --O-- or
--COO--, and A+ represents an organic counter ion.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0013]The present resist composition comprises a resin comprising a
structural unit having an acid-labile group in a side chain and an acid
generator, and the resin contains 40 to 90% by mole of the structural
unit having an acid-labile group in a side chain based on total molar
amounts of all the structural units, and the structural unit having an
acid-labile group in a side chain contains a structural unit represented
by the formula (I):

##STR00006##

(hereinafter, simply referred to as the structural unit (I)).

[0014]The resin preferably contains 45 to 70% by mole of the structural
unit having an acid-labile group in a side chain based on total molar
amounts of all the structural units.

[0015]In this specification, "an acid-labile group" means a group capable
to eliminate by the action of an acid.

[0016]In the present specification, "ester group" means "a structure
having ester of carboxylic acid". Specifically, "tert-butyl ester group"
is "a structure having tert-butyl ester of carboxylic acid", and may be
described as "--COOC(CH3)3".

[0017]In the formula (I), R1 represents a hydrogen atom or a methyl
group, Z represents a single bond or --(CH2)k--CO--O--, k
represents an integer of 1 to 4, R2 is independently in each
occurrence a C1-C6 alkyl group, and m represents an integer of 0 to 14.

[0018]Examples of the C1-C6 alkyl group include a methyl group, an ethyl
group, a propyl group, an isopropyl group, a butyl group, an isobutyl
group, a sec-butyl group, tert-butyl group, a pentyl group and a hexyl
group, and a methyl group is preferable.

[0019]Z is preferably a single bond.

[0020]Examples of the structural unit (I) include the followings.

##STR00007## ##STR00008## ##STR00009##

[0021]The structural unit (I) is a structural unit having an acid-labile
group in its side chain.

[0022]The content of the structural unit (I) is usually 30 to 100 mol %,
preferably 60 to 100 mol % and more preferably 80 to 100 mol % based on
total molar amounts of all the structural units having an acid-labile
group in its side chain.

[0023]Examples of the acid-labile group include a structure having ester
of carboxylic acid such as an alkyl ester group in which a carbon atom
adjacent to the oxygen atom is quaternary carbon atom, an alicyclic ester
group in which a carbon atom adjacent to the oxygen atom is quaternary
carbon atom, and a lactone ester group in which a carbon atom adjacent to
the oxygen atom is quaternary carbon atom. The "quaternary carbon atom"
means a "carbon atom joined to four substituents other than hydrogen
atom".

[0024]Examples of the acid-labile group include an alkyl ester group in
which a carbon atom adjacent to the oxygen atom is quaternary carbon atom
such as a tert-butyl ester group; an acetal type ester group such as a
methoxymethyl ester, ethoxymethyl ester, 1-ethoxyethyl ester,
1-isobutoxyethyl ester, 1-isopropoxyethyl ester, 1-ethoxypropoxy ester,
1-(2-methoxyethoxy)ethyl ester, 1-(2-acetoxyethoxy)ethyl ester,
1-[2-(1-adamantyloxy)ethoxy]ethyl ester,
1-[2-(1-adamantanecarbonyloxy)ethoxy]ethyl ester, tetrahydro-2-furyl
ester and tetrahydro-2-pyranyl ester group; an alicyclic ester group in
which a carbon atom adjacent to the oxygen atom is quaternary carbon atom
such as an isobornyl ester, 1-alkylcycloalkyl ester, 2-alkyl-2-adamantyl
ester, and 1-(1-adamantyl)-1-alkylalkyl ester group.

(hereinafter, simply referred to as the structural unit (II)) or a
structural unit having an acetal structure, a monothioacetal structure or
a dithioacetal structure in its side chain as the structural unit having
an acid-labile group in a side chain.

[0026]The structural unit (II) is different from the structural unit (I).

[0027]In the formula (II), R3 represents a hydrogen atom or a methyl
group, Z1 represents a single bond or --(CH2)j--CO--O--, j
represents an integer of 1 to 4, R4 represents a C1-C8 alkyl group
or a C3-C8 cycloalkyl group, and ring Z2 represents an unsubstituted
or substituted C3-C30 cyclic hydrocarbon group.

[0028]Examples of the C1-C8 alkyl group include a methyl group, an ethyl
group, a propyl group, an isopropyl group, a butyl group, an isobutyl
group, a sec-butyl group, tert-butyl group, a pentyl group, a hexyl group
and an octyl group, and a methyl group, an ethyl group are preferable.
Examples of the C3-C8 cycloalkyl group include a cyclopropyl group, a
cyclobutyl group, a cyclopentyl group, a cyclohexyl group and a
cyclooctyl group.

[0029]The C3-C30 cyclic hydrocarbon group preferably has no aromatic ring.
Examples of the C3-C30 cyclic hydrocarbon group include a C3-C8
cycloalkyl group such as a cyclopropyl group, a cyclobutyl group, a
cyclopropyl group and a cyclohexyl group, an adamantyl group and a
norbornyl group.

[0030]Preferable examples of the structural unit (II) include the
structural units represented by the formulae (IIa) and (IIb):

##STR00011##

wherein R3, R4 and Z1 are the same as defined above,
R5 is independently in each occurrence a C1-C12 alkyl group or a
C1-C12 alkoxy group, 1 represents an integer of 0 to 14, R6 and
R7 each independently represent a hydrogen atom or a C1-C8
monovalent hydrocarbon group which may have one or more heteroatoms, or
R6 and R7 may be bonded to form a C1-C8 divalent hydrocarbon
group which may have one or more heteroatoms and which forms a ring
together with the adjacent carbon atoms to which R6 and R7 are
bonded, or R6 and R7 may be bonded to form a carbon-carbon
double bond between the carbon atom to which R6 is bonded and the
carbon atom to which R7 is bonded, and p represents an integer of 1
to 3 (hereinafter, simply referred to as the structural unit (IIa),
(IIb), respectively).

[0031]Examples of the C1-C12 alkyl group include a methyl group, an ethyl
group, a propyl group, an isopropyl group, a butyl group, an isobutyl
group, a sec-butyl group, a pentyl group, an isopentyl group, a neopentyl
group, a hexyl group, a heptyl group and an octyl group, and a methyl
group is preferable. Examples of the C1-C12 alkoxy group include a
methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a
butoxy group, an isobutoxy group, a sec-butoxy group, a pentyloxy group,
an isopentyloxy group, a neopentyloxy group, a hexyloxy group, a
heptyloxy group and an octyloxy group.

[0032]Examples of the C1-C8 divalent hydrocarbon group formed by bonding
R6 and R7 include an ethylene group and a trimethylene group.

[0033]R6 and R7 are preferably bonded to form a C2-C4 divalent
hydrocarbon group which forms a C4-C6 ring together with the adjacent
carbon atoms to which R6 and R7 are bonded, or R6 and
R7 are preferably bonded to form a carbon-carbon double bond between
the carbon atom to which R6 is bonded and the carbon atom to which
R7 is bonded.

[0034]In the formula (IIa), 1 is preferably 0 or 1, and Z1 preferably
represents a single bond or --CH2--COO--, and more preferably
represents a single bond. In the formula (IIb), p is preferably 1 or 2.

[0035]The resin may have one or more structural units (II). Examples of
the monomer used for giving the structural unit (IIa) include the
followings:

[0040]The monomers giving the structural unit represented by the formula
(IIa), (IIb), (IIc) and (IId) can be produced, for example, by reacting
acrylic halide or methacrylic halide with the corresponding alcohol
compound or its alkali salt.

[0041]While the resin has no structural unit (II), the content of the
structural unit (II) in the resin is preferably 1 to 50 mol %, more
preferably 2 to 30 mol % and especially preferably 2 to 20 mol % based on
total molar amounts of all the structural units having an acid-labile
group in its side chain.

[0042]The acetal structure may be a cyclic acetal structure. The
monothioacetal structure maybe a cyclic structure. The dithioacetal
structure may be a cyclic structure. A monothioacetal structure is
preferable and a cyclic monothioacetal structure is more preferable.

[0043]Examples of the structural unit having an acetal structure, a
monothioacetal structure or a dithioacetal structure in its side chain
include a structural unit represented by the formula (XIII):

##STR00046##

wherein R15 represents a hydrogen atom, a halogen atom, a C1-C4 alkyl
group or a C1-C4 perfluoroalkyl group, Z5 represents a single bond
or --(CH2)s--CO--X4--, s represents an integer of 1 to 4,
X1, X2, X3 and X4 each independently represents an
oxygen atom or a sulfur atom, q represents an integer of 1 to 3 and r
represents an integer of 0 to 3 (hereinafter, simply referred to as the
structural unit (XIII)).

[0044]Examples of the halogen atom include a fluorine atom. Examples of
the C1-C4 alkyl group include a methyl group, an ethyl group, a propyl
group, an isopropyl group, a butyl group and tert-butyl group, and a
methyl group is preferable. Examples of the C1-C4 perfluoroalkyl group
include a trifluoromethyl group, a pentafluoroethyl group, a
heptafluoropropyl group and a nonafluorobutyl group, and a
trifluoromethyl group is preferable. R15 is preferably a hydrogen
atom, a C1-C4 alkyl group or a C1-C4 perfluoroalkyl group, and is more
preferably a hydrogen atom, a methyl group or a trifluoromethyl group.

[0045]X1, X2 and X4 are preferably oxygen atoms or a sulfur
atom, and X3 is preferably a sulfur atom.

[0046]In the formula (XIII), q is preferably 1 and r is preferably 0, 1 or
2.

[0047]Examples of a monomer used for giving the structural unit (XIII)
include the followings:

##STR00047## ##STR00048## ##STR00049##

[0048]These monomers can be produced by reacting the corresponding alcohol
compounds with acryloyl chloride, methacryloyl chloride, acrylic
anhydride or methacrylic anhydride.

[0049]The resin preferably contains 1 to 50 mol % of the structural unit
(XIII), more preferably 2 to 30 mol % of the structural unit (XIII) and
especially preferably 2 to 20 mol % of the structural unit (XIII) based
on total molar amounts of all the structural units having an acid-labile
group in its side chain.

[0050]The resin may have a structural unit having a hydroxyl group in a
side chain, and preferably has a structural unit having a hydroxyl group
in a side chain. In the present specification, --OH of a carboxyl group
is not a hydroxyl group.

[0051]Examples of the structural unit having a hydroxyl group in a side
chain include the following structural unit represented by the formula
(III):

##STR00050##

wherein R8 represents a hydrogen atom or a methyl group, R9 and
R10 each independently represents a hydrogen atom, a methyl group or
a hydroxyl group, R11 represents a methyl group, n' represents an
integer of 0 to 12, Z2 represents a single bond or a
--(CH2)s'--COO-- group, and s' represents an integer of 1 to 4
(hereinafter, simply referred to as the structural unit (III)).

[0052]Z2 preferably represents a single bond or --CH2--COO--,
and n' is preferably 0.

[0053]The resin may have two or more kinds of the structural unit (III),

[0054]Examples of the monomer used for giving the structural unit (III)
include the followings.

[0055]Among these monomers, 3-hydroxy-1-adamantyl acrylate,
3,5-dihydroxy-1-adamantyl acrylate, 3-hydroxy-1-adamantyl methacrylate,
3,5-dihydroxy-1-adamantyl methacrylate,
1-(3-hydroxy-1-adamantyloxycarbonyl)methyl methacrylate and
1-(3,5-dihydroxy-1-adamantyloxycarbony)methyl methacrylate are preferable
since excellent resolution is obtained when the resin containing the
structural unit derived from such monomer is used in the present resist
composition.

[0056]3-Hydroxy-1-adamantyl acrylate, 3,5-dihydroxy-1-adamantyl acrylate,
3-hydroxy-1-adamantyl methacrylate and
3,5-dihydroxy-1-adamantylmethacrylate can be produced, for example, by
reacting corresponding hydroxyl-substituted adamantane with acrylic acid,
methacrylic acid, or its acid halide, and they are also commercially
available.

[0057]The content of the structural unit (III) is preferably 1 to 40 mol %
and more preferably 5 to 35 mol % based on total molar amounts of all the
structural units.

[0058]The resin may have one or more structural units having a lactone
structure. The resin preferably has one or more structural units having a
lactone structure.

[0059]Examples of the structural unit having a lactone structure include a
structural unit having a β-butyrolactone structure, a structural
unit having a γ-butyrolactone structure, a structural unit having a
cycloalkanelactone structure and a structural unit having a
norbornanelactone structure.

[0060]Examples of the structural units having a lactone structure include
a structural unit represented by the formula (IV):

##STR00057##

wherein R12 represents a hydrogen atom or a methyl group, Z3
represents a single bond or --(CH2)i--CO--O--, i represents an
integer of 1 to 4, and ring Z4 represents an unsubstituted or
substituted C3-C30 cyclic hydrocarbon group having --CO--O-- in the ring
structure.

[0061]As the structural unit having a lactone structure, the structural
units represented by the following formulae (IVa), (IVb) and (IVc):

##STR00058##

wherein R12 and Z3 are the same as defined above, and R13
represents a methyl group, R14 is independently in each occurrence a
carboxyl group, a cyano group or a C1-C4 hydrocarbon group, u represents
an integer of 0 to 5 and v represents an integer of 0 to 9, are
preferable.

[0062]Examples of the C1-C4 hydrocarbon group include a methyl group, an
ethyl group, a propyl group, an isopropyl group, a butyl group, an
isobutyl group and a tert-butyl group.

[0063]R14 preferably represents a methyl group, a carboxyl group or a
cyano group, and u is preferably 0, 1 or 2, and v is preferably 0, 1 or
2.

[0064]Examples of the monomers used for giving the structural units
represented by the formulae (IVa), (IVb) and (IVc) include the
followings.

[0065]The resin may contain two or more structural units selected from the
group consisting of the structural units (IVa), (IVb) and (IVc).

[0066]Among the structural units (IVa), (IVb) and (IVc), the structural
unit (IVa) is preferable. The structural units derived from
hexahydro-2-oxo-3,5-methano-2H-cyclopenta[b]furan-6-yl acrylate,
hexahydro-2-oxo-3,5-methano-2H-cyclopenta[b]furan-6-yl methacrylate,
tetrahydro-2-oxo-3-furyl acrylate, tetrahydro-2-oxo-3-furyl methacrylate,
2-(5-oxo-4-oxatricyclo[4.2.1.03.7]nonan-2-yloxy)-2-oxoethyl acrylate
and 2-(5-oxo-4-oxatricyclo[4.2.1.03.7]nonan-2-yloxy)-2-oxoethyl
methacrylate are preferable in viewpoint of the adhesiveness of resist
composition to a substrate.

[0067]The monomers used for giving the structural units represented by the
formulae (Iva), (IVb) and (IVc) can usually be produced by a reaction of
the corresponding hydroxyl-containing lactone compound with an acrylic
halide or methacrylic halide.

[0068]The content of the structural unit (IV) is preferably 1 to 50 mol %
and more preferably 10 to 50 mol % based on total molar amounts of all
the structural units of the resin.

[0069]The resin itself is insoluble or poorly soluble in an alkali aqueous
solution but becomes soluble in an alkali aqueous solution by the action
of an acid.

[0070]The resin has usually a polystyrene-equivalent weight-average
molecular weight of 1,000 to 500,000 and preferably of 2,000 to 50,000.

[0071]The resin can be produced by conducting the polymerization reaction
of the corresponding monomer or monomers. The resin can be also produced
by conducting the oligomerization reaction of the corresponding monomer
or monomers followed by polymerizing the oligomer obtained.

[0072]The polymerization reaction is usually carried out in the presence
of a radical initiator.

[0073]The radical initiator is not limited and examples thereof include an
azo compound such as 2,2'-azobisisobutyronitrile,
2,2'-azobis(2-methylbutyronitrile),
1,1'-azobis(cyclohexane-1-carbonitrile),
2,2'-azobis(2,4-dimethylvaleronitrile),
2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile),
dimethyl-2,2'-azobis(2-methylpropionate) and
2,2'-azobis(2-hydroxymethylpropionitrile); an organic hydroperoxide such
as lauroyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide,
tert-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl
peroxydicarbonate, di-n-propyl peroxydicarbonate, tert-butyl
peroxyneodecanoate, tert-butyl peroxypivalate and 3,5,5-trimethylhexanoyl
peroxide; and an inorganic peroxide such as potassium peroxodisulfate,
ammonium peroxodisulfate and hydrogen peroxide. Among them, the azo
compound is preferable and 2,2'-azobisisobutyronitrile,
2,2'-azobis(2-methylbutyronitrile),
1,1'-azobis(cyclohexane-1-carbonitrile),
2,2'-azobis(2,4-dimethylvaleronitrile) and
dimethyl-2,2'-azobis(2-methylpropionate) are more preferable, and
2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile)
are especially preferable.

[0074]These radical initiators may be used alone or in a form of a mixture
of two or more kinds thereof. When the mixture of two or more kinds
thereof is used, the mixed ratio is not limited.

[0075]The amount of the radical initiator is preferably 1 to 20% by mole
based on all monomer or oligomer molar amounts.

[0076]The polymerization temperature is usually 0 to 150° C., and
preferably 40 to 100° C.

[0077]The polymerization reaction is usually carried out in the presence
of a solvent and it is preferred to use a solvent which is sufficient to
dissolve the monomer, the radical initiator and the resin obtained.
Examples thereof include a hydrocarbon solvent such as toluene; an ether
solvent such as 1,4-dioxane and tetrahydrofuran; a ketone solvent such as
methyl isobutyl ketone; an alcohol solvent such as isopropyl alcohol; a
cyclic ester solvent such as γ-butyrolactone; a glycol ether ester
ester solvent such as propylene glycol monomethyl ether acetate; and an
acyclic ester solvent such as ethyl lactate. These solvents may be used
alone and a mixture thereof may be used.

[0078]The amount of the solvent is not limited, and practically, it is
preferably 1 to 5 parts by weight relative to 1 part of all monomers or
oligomers.

[0079]When an alicyclic compound having an olefinic double bond and an
aliphatic unsaturated dicarboxylic anhydride are used as monomers, it is
preferable to use them in excess amount in view of a tendency that these
are not easily polymerized.

[0080]After completion of the polymerization reaction, the resin produced
can be isolated, for example, by adding a solvent in which the resin is
insoluble or poorly soluble to the reaction mixture obtained and
filtering the precipitated resin. If necessary, the isolated resin may be
purified, for example, by washing with a suitable solvent.

[0082]The acid generator is a substance which is decomposed to generate an
acid by applying a radiation such as a light, an electron beam or the
like on the substance itself or on a resist composition containing the
substance. The acid generated from the acid generator acts on the resin
resulting in cleavage of the acid-labile group existing in the resin.

[0083]Examples of the acid generator include an onium salt compound, an
organo-halogen compound, a sulfone compound, a sulfonate compound, and
the like. The onium salt compound is preferable. The acid generators
described in JP 2003-5374 A such as an acid generator represented by the
following formula:

##STR00074##

can be used.

[0084]A compound represented by the formula:

A+B31

wherein A+ represents an organic counter cation and Brepresents a counter anion, are also used as an acid generator. Examples
of the counter anion include BF4.sup.-, AsF6.sup.-,
PF6.sup.-, SbF6.sup.-, SiF62-, ClO4.sup.-, a
perfluoroalkanesulfonic acid anion such as CF3SO3.sup.-,
pentafluorobenzenesulfonic acid anion, a condensed polynuclear aromatic
sulfonic acid anion such as naphthalene-1-sulfonic acid anion,
anthraquinonesulfonic acid anion, and a dye containing a sulfonic acid
group. Additionally, anions described in JP 2003-5374 A1 such as an anion
represented by the following formula:

##STR00075##

are also listed as the counter anion.

[0085]Examples of the preferable acid generator include a salt represented
by the formula (V):

##STR00076##

(hereinafter, simply referred to as Salt (V)).

[0086]In the formula (V), Y1 and Y2 each independently represent
a fluorine atom or a C1-C6 perfluoroalkyl group, R90 representsa
C1-C36 hydrocarbon group which may have at least one selected from the
group consisting of a C1-C6 alkoxy group, a C1-C4 perfluoroalkyl group, a
C1-C6 hydroxyalkyl group, a hydroxyl group and a cyano group, and one or
more --CH2-- in the hydrocarbon group may be replaced by --CO--,
--O-- or --COO--, and A+ represents an organic counter ion.

[0087]Examples of the C1-C6 perfluoroalkyl group represented by Y1
and Y2 include a trifluoromethyl group, a pentafluoroethyl group, a
heptafluoropropyl group, a nonafluorobutyl group, an undecafluoropentyl
group and a tridecafluorohexyl group, and a trifluoromethyl group is
preferable. Y1 and Y2 each independently is preferably a
fluorine atom or a trifluoromethyl group, and is more preferably fluorine
atoms.

[0088]The C1-C36 hydrocarbon group represented by R40 may have an
alicyclic structure or structures and may have an aromatic group or
groups. The C1-C36 hydrocarbon group may have a carbon-carbon double bond
or bonds. Examples of the C1-C36 hydrocarbon group include a C1-C6 alkyl
group such as a methyl group, an ethyl group, a propyl group, an
isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a
tert-butyl group, a pentyl group and a hexyl group, a C3-C36 saturated
cyclic hydrocarbon group, a C6-C36 aromatic hydrocarbon group, and a
group combined two groups among the above-mentioned groups.

[0089]Examples of the C1-C6 alkoxy group include a methoxy group, an
ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an
isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy
group and a hexyloxy group. Examples of the C1-C4 perfluoroalkyl group
include a trifluoromethyl group, a pentafluoroethyl group, a
heptafluoropropyl group and a nonafluorobutyl group.

[0090]Specific examples of the anion part of Salt (V) include the
followings.

wherein Y1, Y2 and A+ are the same meanings as defined
above, Z' represents a single bond or a C1-C4 alkylene group, and X'
represents a C3-C30 monocyclic or polycyclic hydrocarbon group having a
hydroxyl group or a carbonyl group, and one or more hydrogen atoms in the
monocyclic or polycyclic hydrocarbon group may be replaced by a C1-C6
alkoxy group, a C1-C4 perfluoroalkyl group, a C1-C6 hydroxyalkyl group, a
hydroxyl group or a cyano group (hereinafter, simply referred to as Salt
(VI)) is preferable.

[0092]Examples of the C1-C6 alkoxy group, the C1-C4 perfluoroalkyl group
and the C1-C6 hydroxyalkyl group in X' include the same groups as
described above, respectively.

[0093]Examples of the C1-C4 alkylene group in Z' include a methylene
group, an ethylene group, a trimethylene group and a tetramethylene
group. Z' is preferably a single bond, a methylene group or an ethylene
group, and is more preferable a single bond or a methylene group.

[0094]Examples of X' include a C4-C8 cycloalkyl group such as a cyclobutyl
group, a cyclopentyl group, a cyclohexyl group and a cyclooctyl group, an
adamantyl group, and a norbornyl group, in all of which one or more
hydrogen atoms may be replaced by the C1-06 alkoxy group, the C1-C4
perfluoroalkyl group, the C1-C6 hydroxyalkyl group, a hydroxyl group or a
cyano group.

[0095]Specific examples of X' include a 2-oxocyclopentyl group, a
2-oxocyclohexyl group, a 3-oxocyclopentyl group, a 3-oxocyclohexyl group,
a 4-oxocyclohexyl group, a 2-hydroxycyclopentyl group, a
2-hydroxycyclohexyl group, a 3-hydroxycyclopentyl group, a
3-hydroxycyclohexyl group, a 4-hydroxycyclohexyl group, a
4-oxo-2-adamantyl group, a 3-hydroxy-1-adamantyl group, a
4-hydroxy-1-adamantyl group, a 5-oxonorbornan-2-yl group, a
1,7,7-trimethyl-2-oxonorbornan-2-yl group, a
3,6,6-trimethyl-2-oxo-bicyclo[3.1.1]heptan-3-yl group, a
2-hydroxy-norbornan-3-yl group, a 1,7,7-trimethyl-2-hydroxynorbornan-3-yl
group, a 3,6,6-trimethyl-2-hydroxybicyclo[3.1.1]heptan-3-yl group, and
the following groups (in the following formulae, straight line with an
open end shows a bond which is extended from an adjacent group).

##STR00115##

[0096]Specific examples of the anion part of Salt (VI) include the
followings.

##STR00116## ##STR00117##

[0097]Other examples of the acid generator include a salt represented by
the formula (VIII):

A+-O3S--R52 (VIII)

wherein R52 represents a linear or branched chain C1-C6
perfluoroalkyl group and A+ is the same as defined above
(hereinafter, simply referred to as Salt (VIII)).

[0098]In Salt (VIII), examples of the linear or branched chain C1-C6
perfluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl
group, a heptafluoropropyl group, a nonafluorobutyl group and a
tridecafluorohexyl group.

[0099]Specific examples of the anion part of Salt (VIII) include the
followings.

wherein Pa, Pb and Pc each independently represent a C1-C30
alkyl group or a C3-C30 cyclic hydrocarbon group, and the alkyl group may
have one or more substituents selected from the group consisting of a
hydroxyl group, a C3-C12 cyclic hydrocarbon group and a C1-C12 alkoxy
group, and the cyclic hydrocarbon group may have one or more substituents
selected from the group consisting of a hydroxyl group and a C1-C12
alkoxy group (hereinafter, simply referred to as the cation (IXz)), a
cation represented by the formula (IXb):

##STR00119##

wherein P4 and P5 each independently represent a hydrogen atom,
a hydroxyl group, a C1-C12 alkyl group or a C1-C12 alkoxy group
(hereinafter, simply referred to as the cation (IXb)),a cation
represented by the formula (IXc):

##STR00120##

wherein P6 and P7 each independently represent a C1-C12 alkyl
group or a C3-C12 cycloalkyl group, or P6 and P7 are bonded to
form a C3-C12 divalent acyclic hydrocarbon group which forms a ring
together with the adjacent S+, and one or more --CH2-- in the
divalent acyclic hydrocarbon group may be replaced by --CO--, --O-- or
--S--, P8 represents a hydrogen atom, P9 represents a C1-C12
alkyl group, a C3-C12 cycloalkyl group or an aromatic group which may
have one or more substituents, or P8 and P9 are bonded to form
a divalent acyclic hydrocarbon group which forms a 2-oxocycloalkyl group
together with the adjacent --CHCO--, and one or more --CH2-- in the
divalent acyclic hydrocarbon group may be replaced by --CO--, --O-- or
--S-- (hereinafter, simply referred to as the cation (IXc)); anda cation
represented by the formula (IXd):

[0101]Examples of the C1-C12 alkoxy group in the cations (IXz), (IXb) and
(IXd) include a methoxy group, an ethoxy group, a propoxy group, an
isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group,
a tert-butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy
group and a 2-ethylhexyloxy group.

[0102]Examples of the C3-C12 cyclic hydrocarbon group in the cation (IXz)
include a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, a
2-adamantyl group, a phenyl group, a 2-methylphenyl group, a
4-methylphenyl group, a 1-naphthyl group and a 2-naphthyl group.

[0103]Examples of the C1-C30 alkyl group which may have one or more
substituents selected from the group consisting of a hydroxyl group, a
C3-C12 cyclic hydrocarbon group and a C1-C12 alkoxy group in the cation
(IXz) include a methyl group, an ethyl group, a propyl group, an
isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a
tert-butyl group, a pentyl group, a hexyl group, an octyl group, a
2-ethylhexyl group and a benzyl group.

[0104]Examples of the C3-C30 cyclic hydrocarbon group which may have one
or more substituents selected from the group consisting of a hydroxyl
group and a C1-C12 alkoxy group in the cation (IXz) include a cyclopentyl
group, a cyclohexyl group, a 1-adamantyl group, a 2-adamantyl group, a
bicyclohexyl group, a phenyl group, a 2-methylphenyl group, a
4-methylphenyl group, a 4-ethylphenyl group, a 4-isopropylphenyl group, a
4-tert-butylphenyl group, a 2,4-dimethylphenyl group, a
2,4,6-trimethylphenyl group, a 4-hexylphenyl group, a 4-octylphenyl
group, a 1-naphthyl group, a 2-naphthyl group, a fluorenyl group, a
4-phenylphenyl group, a 4-hydroxyphenyl group, a 4-methoxyphenyl group, a
4-tert-butoxyphenyl group and a 4-hexyloxyphenyl group.

[0105]Examples of the C1-C12 alkyl group in the cations (IXb), (IXc) and
(IXd) include a methyl group, an ethyl group, a propyl group, an
isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a
tert-butyl group, a pentyl group, a hexyl group, an octyl group and a
2-ethylhexyl group.

[0106]Examples of the C3-C12 cycloalkyl group in the cation (IXc) include
a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a
cyclohexyl group, a cycloheptyl group, a cyclooctyl group and a
cyclodecyl group. Examples of the C3-C12 divalent acyclic hydrocarbon
group formed by bonding P6 and P7 include a trimethylene group,
a tetramethylene group and a pentamethylene group. Examples of the ring
group formed together with the adjacent S+ and the divalent acyclic
hydrocarbon group include a tetramethylenesulfonio group, a
pentamethylenesulfonio group and oxybisethylenesulfonio group.

[0107]Examples of the aromatic group in the cation (IXc) include a phenyl
group, a tolyl group, a xylyl group, a 4-butylphenyl group, a
4-isobutylphenyl group, a 4-tert-butylphenyl group, a 4-cyclohexylphenyl
group, a 4-phenylphenyl group, a 1-naphthyl group and a 2-naphthyl group.
The aromatic group may have one or more substituents, and examples of the
substituents include a C1-C6 alkoxy group such as a methoxy group, an
ethoxy group, a propoxy group, a butoxy group, a tert-butoxy group and a
hexyloxy group; a C2-C12 acyloxy group such as an acetyloxy group and a
1-adamantylcarbonyloxy group; and a nitro group.

[0108]Examples of the divalent acyclic hydrocarbon group formed by bonding
P8 and P9 include a methylene group, an ethylene group, a
trimethylene group, a tetramethylene group and a pentamethylene group and
examples of the 2-oxocycloalkyl group formed together with the adjacent
--CHCO-- and the divalent acyclic hydrocarbon group include a
2-oxocyclopentyl group and a 2-oxocyclohexyl group.

[0113]Among the cation (IXz), the cation represented by the formula (IXa):

##STR00137##

wherein P1, P2 and P3 each independently represent a
hydrogen atom, a hydroxyl group, a C1-C12 alkyl group or a C1-C12 alkoxy
group, is preferable. Examples of the C1-C12 alkyl group and the C1-C12
alkoxy group include the same as described above.

[0114]As the organic counter ion represented by A+, a cation
represented by the following formulae (IXe):

##STR00138##

wherein P22, P23 and P24 each independently represent a
hydrogen atom or a C1-C4 alkyl group, is also preferable.

[0115]As the Salt (VI), a salt wherein A+ is the cation represented
by the following formulae (IXe) and the anion part is the following:

##STR00139##

a salt wherein A+ is the cation represented by the following formulae
(IXc) and the anion part is the following:

##STR00140##

are preferable.

[0116]Salt (VI) can be produced according to known methods such as a
method described in JP 2007-249192 A1.

[0117]The salts represented by the formulae (Xd) and (Xe):

##STR00141##

are also preferable.

[0118]The salt represented by the formula (Xf):

##STR00142##

wherein P25, P26 and P27 are the same as defined above and
z represents an integer of 1 to 6, is also preferable.

[0119]The present resist composition preferably includes 60 to 99.9% by
weight of the resin and 0.1 to 40% by weight of an acid generator based
on the total amount of the resin and an acid generator.

[0120]In the present resist composition, performance deterioration caused
by inactivation of acid which occurs due to post exposure delay can be
diminished by adding an organic base compound, particularly a
nitrogen-containing organic base compound as a quencher.

[0121]Specific examples of the nitrogen-containing organic base compound
include an amine compound represented by the following formulae:

##STR00143##

wherein T1 and T2 each independently represent a hydrogen atom,
an alkyl group, a cycloalkyl group or an aryl group, and the alkyl,
cycloalkyl and aryl groups may have one or more substituents selected
from the group consisting of a hydroxyl group, an amino group which have
one or two C1-C4 alkyl groups and a C1-C6 alkoxy group, [0122]T3 and
T4 each independently represent a hydrogen atom, an alkyl group, a
cycloalkyl group, an aryl group or an alkoxy group, and the alkyl,
cycloalkyl, aryl and alkoxy groups may have one or more substituents
selected from the group consisting of a hydroxyl group, an amino group
which may have one or more C1-C4 alkyl groups and a C1-C6 alkoxy group,
or T3 and T4 are bonded each other to form an aromatic ring
together with the carbon atoms to which they are bonded, [0123]T5
represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl
group, an alkoxy group or a nitro group, and the alkyl, cycloalkyl, aryl
and alkoxy groups may have one or more substituents selected from the
group consisting of a hydroxyl group, an amino group which may have one
or two C1-C4 alkyl groups and a C1-C6 alkoxy group, [0124]T6
represents an alkyl group or a cycloalkyl group, and the alkyl and
cycloalkyl groups may have one or more substituents selected from the
group consisting of a hydroxyl group, an amino group which may have one
or two C1-C4 alkyl groups and a C1-C6 alkoxy group, and W represents
--CO--, --NH--, --S--, --S--S--, an alkylene group of which one or more
--CH2-- may be replaced by --O--, or an alkenylene group of which
one or more --CH2-- may be replaced by --O--,and a quaternary
ammonium hydroxide represented by the following formula:

##STR00144##

[0124]wherein T7, T8, T9 and T10 each independently
represent an alkyl group, a cycloalkyl group or an aryl group, and the
alkyl, cycloalkyl and aryl groups may have one or more substituents
selected from the group consisting of a hydroxyl group, an amino group
which may have one or two C1-C4 alkyl groups and a C1-C6 alkoxy group.

[0125]The alkyl group in T1, T2, T3, T4, T5,
T6, T7, T8, T9 and T10 preferably has about 1 to
10 carbon atoms, and more preferably has about 1 to 6 carbon atoms.

[0126]Examples of the amino group which may have one or two C1-C4 alkyl
groups include an amino group, a methylamino group, an ethylamino group,
a butylamino group, a dimethylamino group and a diethylamino group.
Examples of the C1-C6 alkoxy group which may be substituted with the
C1-C6 alkoxy group or groups include a methoxy group, an ethoxy group, a
propoxy group, an isopropoxy group, a butoxy group, a tert-butoxy group,
a pentyloxy group, a hexyloxy group and a 2-methoxyethoxy group.

[0127]Specific examples of the alkyl group which may have one or more
substituents selected from the group consisting of a hydroxyl group, an
amino group which may have one or two C1-C4 alkyl groups, and a C1-C6
alkoxy group include a methyl group, an ethyl group, a propyl group, an
isopropyl group, a butyl group, a tert-butyl group, a pentyl group, a
hexyl group, an octyl group, a nonyl group, a decyl group, a
2-(2-methoxyethoxy)ethyl group, a 2-hydroxyethyl group, a 2-hydroxypropyl
group, a 2-aminoethyl group, a 4-aminobutyl group and a 6-aminohexyl
group.

[0128]The cycloalkyl group in T1, T2, T3, T4, T5,
T6, T7, T8, T9 and T10 preferably has about 5 to
10 carbon atoms. Specific examples of the cycloalkyl group which may have
one or more substituents selected from the group consisting of a hydroxyl
group, an amino group which may have one or two C1-C4 alkyl groups and a
C1-C6 alkoxy group include a cyclopentyl group, a cyclohexyl group, a
cycloheptyl group and a cyclooctyl group.

[0129]The aryl group in T1, T2, T3, T4, T5,
T6, T7, T8, T9 and T10 preferably has about 6 to
10 carbon atoms. Specific examples of the aryl group which may have one
or more substituents selected from the group consisting of a hydroxyl
group, an amino group which may have one or two C1-C4 alkyl groups and a
C1-C6 alkoxy group include a phenyl group and a naphthyl group.

[0130]The alkoxy group in T3, T4 and T5 preferably has
about 1 to 6 carbon atoms and specific examples thereof include a methoxy
group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy
group, a tert-butoxy group, a pentyloxy group and a hexyloxy group.

[0131]The alkylene and alkenylene groups in W preferably have 2 to 6
carbon atoms. Specific examples of the alkylene group include an ethylene
group, a trimethylene group, a tetramethylene group, a methylenedioxy
group and an ethylene-1,2-dioxy group, and specific examples of the
alkenylene group include an ethene-1,2-diyl group, a 1-propene-1,3-diyl
group and a 2-butene-1,4-diyl group.

[0134]A hindered amine compound having a piperidine skeleton as disclosed
in JP 11-52575 A1 can be also used as the quencher.

[0135]In the point of forming patterns having higher resolution, the
quaternary ammonium hydroxide is preferably used as the quencher.

[0136]When the basic compound is used as the quencher, the present resist
composition preferably includes 0.01 to 5% by weight of the basic
compound based on the total amount of the solid components.

[0137]The present resist composition can contain, if necessary, a small
amount of various additives such as a sensitizer, a dissolution
inhibitor, other polymers, a surfactant, a stabilizer and a dye as long
as the effect of the present invention is not prevented.

[0138]The present resist composition is usually in the form of a resist
liquid composition in which the above-mentioned ingredients are dissolved
in a solvent and the resist liquid composition is applied onto a
substrate such as a silicon wafer by a conventional process such as spin
coating. The solvent used is sufficient to dissolve the above-mentioned
ingredients, have an adequate drying rate, and give a uniform and smooth
coat after evaporation of the solvent. Solvents generally used in the art
can be used.

[0139]Examples of the solvent include a glycol ether ester such as ethyl
cellosolve acetate, methyl cellosolve acetate and propylene glycol
monomethyl ether acetate; an acyclic ester such as ethyl lactate, butyl
acetate, amyl acetate and ethyl pyruvate; a ketone such as acetone,
methyl isobutyl ketone, 2-heptanone and cyclohexanone; and a cyclic ester
such as γ-butyrolactone. These solvents may be used alone and two
or more thereof may be mixed to use.

[0140]A resist film applied onto the substrate and then dried is subjected
to exposure for patterning, then heat-treated to facilitate a deblocking
reaction, and thereafter developed with an alkali developer. The alkali
developer used may be any one of various alkaline aqueous solution used
in the art. Generally, an aqueous solution of tetramethylammonium
hydroxide or (2-hydroxyethyl)trimethylammonium hydroxide (commonly known
as "choline") is often used.

[0142]It should be construed that embodiments disclosed here are examples
in all aspects and not restrictive. It is intended that the scope of the
present invention is determined not by the above descriptions but by
appended claims, and includes all variations of the equivalent meanings
and ranges to the claims.

[0143]The present invention will be described more specifically by way of
examples, which are not construed to limit the scope of the present
invention. The "%" and "part(s)" used to represent the content of any
component and the amount of any material used in the following examples
and comparative examples are on a weight basis unless otherwise
specifically noted. The weight-average molecular weight of any material
used in the following examples is a value found by gel permeation
chromatography [Column (Three Columns): TSKgel Multipore HXL-M, Solvent:
Tetrahydrofuran, manufactured by TOSOH CORPORATION] using polystyrene as
a standard reference material.

[0144]Monomers used in the following Resin Synthetic Examples are
following monomers M1, M2, M3, M4, M5, M6, M7, M8 and M9.

##STR00145## ##STR00146##

Resin Synthetic Example 1

[0145]Into a flask equipped with a condenser and a thermometer, 10.31
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 29.70 parts of monomer M1, 4.12 parts of
monomer M4, 7.41 parts of monomer M5, 0.29 parts of
2,2'-azobisisobutyronitrile, 1.30 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 30.92 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 65.96 parts of 1,4-dioxane
and the resultant solution was poured into 536 parts of methanol to cause
precipitation. The precipitate was isolated and mixed with 268 parts of
methanol. The resultant mixture was stirred followed by filtrating to
obtain the precipitate. The operation wherein the precipitate was mixed
with 268 parts of methanol and the resultant mixture was stirred followed
by filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 19 parts of a
resin having a weight-average molecular weight (Mw) of 6.7×103
and a dispersion degree (Mw/Mn) of 1.45 in a yield of 46%. This resin had
the structural units represented by the formula A, D and E. This is
called as resin R1. The ratio of the structural units represented by the
formula A, ID and E (A/D/E) was 52/13/35.

##STR00147##

Resin Synthetic Example 2

[0146]Into a flask equipped with a condenser and a thermometer, 21.21
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 72° C. under nitrogen, a
solution obtained by mixing 60.00 parts of monomer M1, 7.09 parts of
monomer M3, 6.55 parts of monomer M4, 11.20 parts of monomer M5, 0.57
parts of 2,2'-azobisisobutyronitrile, 2.58 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 63.63 parts of 1,4-dioxane was
added dropwise thereto over 2 hours at 72° C. The resultant
mixture was stirred for 5 hours at 72° C. After cooling the
reaction mixture, the reaction mixture was diluted with 135.75 parts of
1,4-dioxane and the resultant solution was poured into a mixture of 882
parts of methanol and 221 parts of ion-exchanged water to cause
precipitation. The precipitate was isolated and mixed with 551 parts of
methanol. The resultant mixture was stirred followed by filtrating to
obtain the precipitate. The operation wherein the precipitate was mixed
with 551 parts of methanol and the resultant mixture was stirred followed
by filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 52 parts of a
resin having a weight-average molecular weight (Mw) of 5.9×103
and a dispersion degree (Mw/Mn) of 1.91 in a yield of 62%. This resin had
the structural units represented by the formula A, C, D and E. This is
called as resin R2. The ratio of the structural units represented by the
formula A, C, D and E (A/C/D/E) was 52/10/11/27.

##STR00148##

Resin Synthetic Example 3

[0147]Into a flask equipped with a condenser and a thermometer, 11.51
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 73° C. under nitrogen, a
solution obtained by mixing 30.00 parts of monomer M1, 3.55 parts of
monomer M3, 3.27 parts of monomer M4, 9.22 parts of monomer M6, 0.28
parts of 2,2'-azobisisobutyronitrile, 1.29 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 34.53 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 73° C. The resultant mixture
was stirred for 5 hours at 73° C. After cooling the reaction
mixture, the reaction mixture was diluted with 73.67 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 479 parts of
methanol and 120 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 299 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 299
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 27 parts of a
resin having a weight-average molecular weight (Mw) of 7.7×103
and a dispersion degree (Mw/Mn) of 1.87 in a yield of 60%. This resin had
the structural units represented by the formula A, C, D and F. This is
called as resin R3. The ratio of the structural units represented by the
formula A, C, D and F (A/C/D/F) was 54/9/11/26.

##STR00149##

Comparative Resin Synthetic Example 1

[0148]Into a flask equipped with a condenser and a thermometer, 70.91
parts of methyl isobutyl ketone was charged and a nitrogen gas was blown
into it for 30 minutes. After heating it up to 87° C. under
nitrogen, a solution obtained by mixing 30.00 parts of monomer M2, 14.27
parts of monomer M4, 10.28 parts of monomer M5, 0.79 parts of
2,2'-azobisisobutyronitrile and 70.91 parts of methyl isobutyl ketone was
added dropwise thereto over 2 hours at 87° C. The resultant
mixture was stirred for 6 hours at 87° C. After cooling the
reaction mixture, the reaction mixture was poured into a mixture of 895
parts of methanol and 196 parts of ion-exchanged water to cause
precipitation. The precipitate was isolated and mixed with 344 parts of
methanol. The resultant mixture was stirred followed by filtrating to
obtain the precipitate. The operation wherein the precipitate was mixed
with 344 parts of methanol and the resultant mixture was stirred followed
by filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 25 parts of a
resin having a weight-average molecular weight (Mw) of 9.4×103
and a dispersion degree (Mw/Mn) of 1.52 in a yield of 47%. This resin had
the structural units represented by the formula B, D and E. This is
called as resin R4. The ratio of the structural units represented by the
formula B, D and E (B/D/E) was 33/33/34.

##STR00150##

Resin Synthetic Example 4

[0149]Into a flask equipped with a condenser and a thermometer, 23.97
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 17.50 parts of monomer M1, 4.91 parts of
monomer M7, 3.94 parts of monomer M4, 9.35 parts of monomer M6, 4.26
parts of monomer M5, 0.27 parts of 2,2'-azobisisobutyronitrile, 1.24
parts of 2,2'-azobis(2,4-dimethylvaleronitrile) and 35.96 parts of
1,4-dioxane was added dropwise thereto over 1 hour at 75° C. The
resultant mixture was stirred for 5 hours at 75° C. After cooling
the reaction mixture, the reaction mixture was diluted with 43.95 parts
of 1,4-dioxane and the resultant solution was poured into a mixture of
415 parts of methanol and 104 parts of ion-exchanged water to cause
precipitation. The precipitate was isolated and mixed with 260 parts of
methanol. The resultant mixture was stirred followed by filtrating to
obtain the precipitate. The operation wherein the precipitate was mixed
with 260 parts of methanol and the resultant mixture was stirred followed
by filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 30 parts of a
resin having a weight-average molecular weight (Mw) of 7.5×103
and a dispersion degree (Mw/Mn) of 1.90 in a yield of 74%. This resin had
the structural units represented by the formula A, G, D, F and E. This is
called as resin R5. The ratio of the structural units represented by the
formula A, G, D, F and E (A/G/D/F/E) was 29/15/12/25/19.

##STR00151##

Resin Synthetic Example 5

[0150]Into a flask equipped with a condenser and a thermometer, 24.04
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 73° C. under nitrogen, a
solution obtained by mixing 18.00 parts of monomer M1, 2.09 parts of
monomer M7, 2.88 parts of monomer M4, 17.09 parts of monomer M6, 0.25
parts of 2,2'-azobisisobutyronitrile, 1.14 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 36.06parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 73° C. The resultant mixture
was stirred for 5 hours at 73° C. After cooling the reaction
mixture, the reaction mixture was diluted with 44.07 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 415 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 260 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 260
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 28 parts of a
resin having a weight-average molecular weight (Mw) of 7.1×103
and a dispersion degree (Mw/Mn) of 1.82 in a yield of 69%. This resin had
the structural units represented by the formula A, G, D and F. This is
called as resin R6. The ratio of the structural units represented by the
formula A, G, D and F (A/G/D/F) was 33/7/10/50.

##STR00152##

Resin Synthetic Example 6

[0151]Into a flask equipped with a condenser and a thermometer, 24.04
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 18.50 parts of monomer M1, 3.01 parts of
monomer M7, 3.09 parts of monomer M8, 15.46 parts of monomer M6, 0.25
parts of 2,2'-azobisisobutyronitrile, 1.14 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 36.06 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 44.07 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 417 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 260 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 260
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 29 parts of a
resin having a weight-average molecular weight (Mw) of 7.3×103
and a dispersion degree (Mw/Mn) of 1.66 in a yield of 73%. This resin had
the structural units represented by the formula A, G, H and F. This is
called as resin R7. The ratio of the structural units represented by the
formula A, G, H and F (A/G/H/F) was 35/10/10/45.

##STR00153##

Resin Synthetic Example 7

[0152]Into a flask equipped with a condenser and a thermometer, 19.18
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 22.80 parts of monomer M1, 3.41 parts of
monomer M7, 10.47 parts of monomer M9, 3.29 parts of monomer M4, 0.29
parts of 2,2'-azobisisobutyronitrile, 1.29 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 28.77 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 55.95 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 416 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 260 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 260
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 28 parts of a
resin having a weight-average molecular weight (Mw) of 7.1×103
and a dispersion degree (Mw/Mn) of 2.01 in a yield of 71%. This resin had
the structural units represented by the formula A, G, I and D. This is
called as resin R8. The ratio of the structural units represented by the
formula A, G, I and D (A/G/I/D) was 41/10/39/10.

##STR00154##

Resin Synthetic Example 8

[0153]Into a flask equipped with a condenser and a thermometer, 19.17
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 21.50 parts of monomer M1, 5.55 parts of
monomer M9, 3.31 parts of monomer M8, 7.35 parts of monomer M6, 2.23
parts of monomer M5, 0.27 parts of 2,2'-azobisisobutyronitrile, 1.22
parts of 2,2'-azobis(2,4-dimethylvaleronitrile) and 28.76 parts of
1,4-dioxane was added dropwise thereto over 1 hour at 75° C. The
resultant mixture was stirred for 5 hours at 75° C. After cooling
the reaction mixture, the reaction mixture was diluted with 55.92 parts
of 1,4-dioxane and the resultant solution was poured into a mixture of
415 parts of methanol and 104 parts of ion-exchanged water to cause
precipitation. The precipitate was isolated and mixed with 260 parts of
methanol. The resultant mixture was stirred followed by filtrating to
obtain the precipitate. The operation wherein the precipitate was mixed
with 260 parts of methanol and the resultant mixture was stirred followed
by filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 30 parts of a
resin having a weight-average molecular weight (Mw) of 7.7×103
and a dispersion degree (Mw/Mn) of 1.76 in a yield of 74%. This resin had
the structural units represented by the formula A, I, H, F and E. This is
called as resin R9. The ratio of the structural units represented by the
formula A, I, H, F and E (A/I/H/F/E) was 39/22/10/19/10.

##STR00155##

Resin Synthetic Example 9

[0154]Into a flask equipped with a condenser and a thermometer, 14.39
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 19.50 parts of monomer M1, 4.35 parts of
monomer M3, 2.81 parts of monomer M4, 13.33 parts of monomer M6, 0.24
parts of 2,2'-azobisisobutyronitrile, 1.11 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 33.59 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 55.98 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 416 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 260 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 260
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 28 parts of a
resin having a weight-average molecular weight (Mw) of 8.2×103
and a dispersion degree (Mw/Mn) of 1.86 in a yield of 71%. This resin had
the structural units represented by the formula A, C, D and F. This is
called as resin R10. The ratio of the structural units represented by the
formula A, C, D and F (A/C/D/F) was 39/12/10/39.

##STR00156##

Resin Synthetic Example 10

[0155]Into a flask equipped with a condenser and a thermometer, 10.01
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 25.40 parts of monomer M1, 4.16 parts of
monomer M4, 10.48 parts of monomer M5, 0.29 parts of
2,2'-azobisisobutyronitrile, 1.31 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 30.03 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 64.07 parts of 1,4-dioxane
and the resultant solution was poured into 521 parts of methanol to cause
precipitation. The precipitate was isolated and mixed with 260 parts of
methanol. The resultant mixture was stirred followed by filtrating to
obtain the precipitate. The operation wherein the precipitate was mixed
with 260 parts of methanol and the resultant mixture was stirred followed
by filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 21 parts of a
resin having a weight-average molecular weight (Mw) of 7.7×103
and a dispersion degree (Mw/Mn) of 1.48 in a yield of 53%. This resin had
the structural units represented by the formula A, D and E. This is
called as resin R11. The ratio of the structural units represented by the
formula A, D and E (A/D/E) was 43/12/45.

##STR00157##

Resin Synthetic Example 11

[0156]Into a flask equipped with a condenser and a thermometer, 10.00
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 70° C. under nitrogen, a
solution obtained by mixing 35.80 parts of monomer M1, 1.50 parts of
monomer M4, 2.70 parts of monomer M5, 0.26 parts of
2,2'-azobisisobutyronitrile, 1.18 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 30.00 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 70° C. The resultant mixture
was stirred for 5 hours at 70° C. After cooling the reaction
mixture, the reaction mixture was diluted with 64.00 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 416 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 260 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 260
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 18 parts of a
resin having a weight-average molecular weight (Mw) of 4.3×103
and a dispersion degree (Mw/Mn) of 1.65 in a yield of 46%. This resin had
the structural units represented by the formula A, D and E. This is
called as resin R12. The ratio of the structural units represented by the
formula A, D and E (A/D/E) was 75/7/18.

##STR00158##

Resin Synthetic Example 12

[0157]Into a flask equipped with a condenser and a thermometer, 19.16
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 20.00 parts of monomer M1, 2.99 parts of
monomer M7, 1.54 parts of monomer M8, 15.38 parts of monomer M6, 0.25
parts of 2,2'-azobisisobutyronitrile, 1.14 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 28.74 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 55.88 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 415 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 259 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 259
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 29 parts of a
resin having a weight-average molecular weight (Mw) of 7.5×103
and a dispersion degree (Mw/Mn) of 1.83 in a yield of 72%. This resin had
the structural units represented by the formula A, G, H and F.

[0158]This is called as resin R13. The ratio of the structural units
represented by the formula A, G, H and F (A/G/H/F) was 39/11/5/45.

##STR00159##

Resin Synthetic Example 13

[0159]Into a flask equipped with a condenser and a thermometer, 19.21
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 21.40 parts of monomer M1, 3.20 parts of
monomer M7, 1.65 parts of monomer M8, 9.60 parts of monomer M6, 4.16
parts of monomer M5, 0.25 parts of 2,2'-azobisisobutyronitrile, 1.15
parts of 2,2'-azobis(2,4-dimethylvaleronitrile) and 28.81 parts of
1,4-dioxane was added dropwise thereto over 1 hour at 75° C. The
resultant mixture was stirred for 5 hours at 75° C. After cooling
the reaction mixture, the reaction mixture was diluted with 56.02 parts
of 1,4-dioxane and the resultant solution was poured into a mixture of
416 parts of methanol and 104 parts of ion-exchanged water to cause
precipitation. The precipitate was isolated and mixed with 260 parts of
methanol. The resultant mixture was stirred followed by filtrating to
obtain the precipitate. The operation wherein the precipitate was mixed
with 260 parts of methanol and the resultant mixture was stirred followed
by filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 28 parts of a
resin having a weight-average molecular weight (Mw) of 7.1×103
and a dispersion degree (Mw/Mn) of 1.83 in a yield of 71%. This resin had
the structural units represented by the formula A, G, H, F and

[0160]E. This is called as resin R14. The ratio of the structural units
represented by the formula A, G, H, F and E (A/G/H/F/E) was
39/10/5/27/19.

##STR00160##

Resin Synthetic Example 14

[0161]Into a flask equipped with a condenser and a thermometer, 10.01
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 24.90 parts of monomer M1, 2.96 parts of
monomer M4, 12.19 parts of monomer M5, 0.29 parts of
2,2'-azobisisobutyronitrile, 1.33 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 30.04 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 64.08 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 417 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 260 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 260
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 28 parts of a
resin having a weight-average molecular weight (Mw) of 6.7×103
and a dispersion degree (Mw/Mn) of 1.75 in a yield of 70%. This resin had
the structural units represented by the formula A, D and E. This is
called as resin R15. The ratio of the structural units represented by the
formula A, D and E (A/D/E) was 41/9/50.

##STR00161##

Resin Synthetic Example 15

[0162]Into a flask equipped with a condenser and a thermometer, 19.18
parts of 1,4-dioxane was charged and a nitrogen gas was blown into it for
30 minutes. After heating it up to 75° C. under nitrogen, a
solution obtained by mixing 23.60 parts of monomer M1, 3.53 parts of
monomer M7, 1.82 parts of monomer M8, 11.02 parts of monomer M5, 0.30
parts of 2,2'-azobisisobutyronitrile, 1.34 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) and 28.78 parts of 1,4-dioxane was
added dropwise thereto over 1 hour at 75° C. The resultant mixture
was stirred for 5 hours at 75° C. After cooling the reaction
mixture, the reaction mixture was diluted with 55.95 parts of 1,4-dioxane
and the resultant solution was poured into a mixture of 416 parts of
methanol and 104 parts of ion-exchanged water to cause precipitation. The
precipitate was isolated and mixed with 260 parts of methanol. The
resultant mixture was stirred followed by filtrating to obtain the
precipitate. The operation wherein the precipitate was mixed with 260
parts of methanol and the resultant mixture was stirred followed by
filtrating to obtain the precipitate was repeated twice. The obtained
precipitate was dried under reduced pressure to obtain 27 parts of a
resin having a weight-average molecular weight (Mw) of 6.1×103
and a dispersion degree (Mw/Mn) of 1.81 in a yield of 68%. This resin had
the structural units represented by the formula A, G, H and E. This is
called as resin R16. The ratio of the structural units represented by the
formula A, G, H and E (A/G/H/E) was 39/10/5/46.

[0168]The following components were mixed and dissolved, further,
filtrated through a nylon filter having pore diameter of 0.2 μm, a
fluorine resin filter having pore diameter of 0.1 μm and a
polyethylene filter having pore diameter of 0.03 μm, to prepare resist
composition. [0169]Resin (kind and amount are described in Table 1)
[0170]Acid generator (kind and amount are described in Table 1)
[0171]Quencher (kind and amount are described in Table 1) [0172]Solvent
(kind is described in Table 1)

[0173]Silicon wafers were each coated with "ARC-29A", which is an organic
anti-reflective coating composition available from Nissan Chemical
Industries, Ltd., and then baked under the conditions: 205° C., 60
seconds, to form a 780 Å-thick organic anti-reflective coating. Each
of the resist liquids prepared as above was spin-coated over the
anti-reflective coating so that the thickness of the resulting film
became 150 nm after drying. The silicon wafers thus coated with the
respective resist liquids were each prebaked on a direct hotplate at
110° C. for 60 seconds. Using an ArF excimer stepper
("FPA5000-AS3" manufactured by CANON INC., NA=0.75, σ=0.85), each
wafer thus formed with the respective resist film was subjected to
contact hole pattern exposure, with the exposure quantity being varied by
0.5 mJ/cm2.

[0174]After the exposure, each wafer was subjected to post-exposure baking
on a hotplate at a temperature shown in column of "PEB" of Table 1 for 60
seconds and then to paddle development for 60 seconds with an aqueous
solution of 2.38wt % tetramethylammonium hydroxide.

[0175]Each of hole patterns developed on the organic anti-reflective
coating substrate after the development was observed with a scanning
electron microscope, the results of which are shown in Tables 2.

[0176]Effective Sensitivity (ES): It was expressed as the amount of
exposure that hole diameter of the hole pattern became 110 nm after
exposure using a mask having a pitch of 210 nm and a hole diameter of 130
nm and development.

[0177]Mask Error Enhancement Factor (MEEF): Hole diameters of each hole
patterns exposed at ES using masks having a pitch of 210 nm and a hole
diameter of 125 to 135 nm with 1 nm increments in between and developed
were measured. Hole diameters measured were plotted against the hole
diameters of masks, and the slope of the line was calculated. MEEF was
expressed as the value of the slope of the line. The smaller the value
is, the better MEEF is.

[0178]Pattern Profile: The hole patterns after exposure using a mask
having a pitch of 210 nm and a hole diameter of 140 nm and development
were observed with a scanning electron microscope. In one filed of the
scanning electron microscope, 25 holes were observed, and when
neighboring holes were connected, resolution is bad and its evaluation is
marked by "×", and when neighboring holes were not connected,
resolution is good and its evaluation is marked by "◯".